SEQUENTIAL SEPARATION AND DETERMINATION OF PLUTONIUM, AM-241 AND SR-90 IN SOILS AND SEDIMENTS

A sensitive and reliable method for the sequential separation and dete rmination of plutonium, Am-241 and Sr-90 in soil samples was developed . Plutonium was separated by a Microthene-TNOA column. Then Y-90 (for Sr-90 determination) was separated from americium by a HDEHP column af ter elimination of large amounts of interfering stable or radioactive nucIides (iron, Bi-210 and Po-210 etc.) by an oxalate precipitation an d a Microthene-TNOA column. Finally americium was purified by another HDEHP column and a PMBP-TOPO extraction. A special attention was paid to the decontamination of Pu and Am from Po-210 and of Y-90 from Bi-21 0; the relevant decontamination factors resulted greater than 10(5), 1 0(6) and 10(4) respectively. The detection limits were 1.2 mBq/kg for Pu and 1.7 mBq/kg for Am-241 and 0.32 Bq/kg for Sr-90. The procedure w as checked by analyzing three certified samples supplied by IAEA. Some Italian soil samples were also analyzed giving average yields of 84.9 +/-7.2% for Pu, 57.8+/-3.2% for Am and 96.7+/-1.6% for Y; the Pu239+24 0, Pu-238, Am-241 and Sr-90 contents (Bq/kg) ranged from 0.347 to 1.53 , from 0.013 to 0.048, from 0.126 to 0.556 and from 2.89 to 11.6 respe ctively and the average ratios were 0.037+/-0.017 for Pu-238/Pu239+240 , 0.357+/-0.040 for Am-241/Pu239+240 and 7.0+/-1.2 for Sr-90/Pu239+240 .